In biomedical research monitoring processes in living organisms is a constant focus.
Extracting blood or other body fluids from patients in order to diagnose disease states or monitor physiological conditions have applications in both intensive care hospital medicine, managing disease and interventions and in research.
Methods to monitor contents of analytes in blood generally involve accessing the circulation of the patient through a catheter venflon needle or other means.
The most common method is to extract a sample using a needle and vacuum tube whenever a blood parameter needs to be evaluated.
For many blood constituents this approach is sufficient especially where the concentration of blood analytes are fairly stable and only infrequent samples need be taken.
For more labile blood constituents, such as glucose, metabolic markers, hormones and other signalling molecules such as adrenaline and cortisol the concentrations may change rapidly within a short time frame and may even be directly influenced by the sampling procedure itself.
If blood concentration of these constituents are to be frequently determined either frequent manual blood samples must be taken or an automatic sampling system used.
Where samples must be taken continuously or at relatively small intervals the catheter can advantageously be inserted permanently into the vessel however problems may arise due to clogging of the lumen and/or opening of the catheter or any attached devices.